What oral meds are you taking? If you have never taken any mesalamine/Asacol meds before then your reaction to the enema could mean you are sensitive to the drug itself
or you could be reacting to something in the enema suspension. Rowasa is also available in a sulfate-free version(or sulphite-free I can not remember which is which). It's called Rowasa-sf I think.
If I were you I'd stop the enema and see if your flu symptoms stop. Then you'll know what to do next. If you get the Rowsasa-sf and have the same reaction then you are allergic to mesalamine. If the Rowasa-sf works then you are allergic to the suspension liquid.
If you are already taking oral mesalamine it's probably the suspension liquid causing problems.
Begin detective work on yourself.
Good luck.